This invention relates to regulators for auxiliary air injection at the intake of internal combustion engines. Devices of this type are known and employed to correct the inadequate operational accuracy of conventional carburetors. One such prior art device is described in my French Pat. No. 74 32501, which discloses the use of an analyzing probe for the exhaust gases which delivers a signal to an electronic device which, through the intermediary of an electric valve, acts on a pneumatic valve controlled by partial vacuum and which regulates the intake downstream of the carburetor. Such systems constitute a control loop which will operate most accurately in the steady state or for very slow operational changes; however, they have generally not operated entirely satisfactorily when there are rapid changes in engine operation. It is, therefore, the object of the present invention to provide an improved regulating device that will operate very precisely even during sudden or rapid operational changes.